PROTOHIPPUS. 



141 



borders simple, fossettes contracted, prefossettes closed early in wear; (4) pli caballin rudimentary; (5) metastylid not 

 separated from metaconid on p 2 ; (6) metaconid-metastylid pillars forming a column narrow at top, broader toward base, 

 separated by a shallow groove, deepening toward base but disappearing before it reaches the base; (7) heel of m 3 small, 

 simple, (8) anterior cingulum prominent on inside and outside of tooth, extending to top of crown as in Hipparion. (9) 

 Malar fossa apparently absent; (10) metatarsals long, slender, lateral digits much reduced; (] 1 ) ungual phalanges rather 

 narrow. 



The milk molars are hypsodont, narrow, fully cemented when little worn, removing this type from Merychippus and 

 placing it within Protohippus. No milk molars of this type are found in the typical Pawnee Creek beds of the Middle 

 Eocene. 



Protohippus castilli Cope 1885. 

 Text Fig. 113. 



Protohippus castilli, sp. nov., Cope, E. D. "Report on the Coal Deposits near Laeualtipan, in the State of Hidalgo, Mexico," 

 Proc. Amer. Philos. Soc. Vol. XXIII, 1886 (sig. dated Dec. 2, 1885), pp. 150-151, fig. 2. "Pliocene Horses of Southwestern Texas," 

 Amer. Naturalist, Vol. XIX, No. 12, Dec, 1885, pp. 1208-1209, PI. xxxvii, fig. 6. 



Horizon and locality . — (Cope, Proc. 1885, p. 150) "From the Loup Fork Shales of Tehuichila, Vera Cruz,". . . [p. 147] 

 Upper Miocene, of Loup Fork age. Type collected by Edward D. Cope. Freudenberg calls this horizon " Upper Miocene 

 or Lower Pliocene." It contains also Hyasnarctos recorded from Pliocene of Florida, Oregon and Nebraska. — W. D. M. 



Fig. 113. Type of Protohippus castilli Cope, Amer. Mus. Cope Coll. S344. (Upper) Original figure of the type. 

 After Cope, 1885, fig. 2, p. 151. (Lower) (1) Crown, (a) external, and (b) anterior views of the type, drawn under the 

 direction of Osborn. All figures natural size. 



Type. — Amer. Mus. Cope Coll. 8344. (Cope, Proc. 1885, p. 150) "This horse is represented by a superior molar tooth 

 of a larger animal than the species last described [H. peninsulatus], and one only a little smaller than the zebra." (Gidley, 

 1907, p. 901) " An upper molar of the left side." Measurements: (Cope) length of crown .040, a.p. .021, tr. .023. 



Type figure. — Text Fig. 113 of this Memoir. 



